CN113224759A - Unified power quality regulator based on wireless power transmission - Google Patents

Unified power quality regulator based on wireless power transmission Download PDF

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Publication number
CN113224759A
CN113224759A CN202110606060.8A CN202110606060A CN113224759A CN 113224759 A CN113224759 A CN 113224759A CN 202110606060 A CN202110606060 A CN 202110606060A CN 113224759 A CN113224759 A CN 113224759A
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China
Prior art keywords
converter
bridge
series
power transmission
frequency
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CN202110606060.8A
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Inventor
王宪萍
王晓东
杨林涛
杜娟
张文晋
李思岑
傅鹏
陈沼宇
倪喜军
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Changzhi Power Supply Co of State Grid Shanxi Electric Power Co Ltd
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Changzhi Power Supply Co of State Grid Shanxi Electric Power Co Ltd
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Priority to CN202110606060.8A priority Critical patent/CN113224759A/en
Publication of CN113224759A publication Critical patent/CN113224759A/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
    • H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J5/00—Circuit arrangements for transfer of electric power between ac networks and dc networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
    • H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
    • H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/30—Reactive power compensation
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/40—Arrangements for reducing harmonics

Abstract

The invention relates to a unified power quality regulator based on wireless power transmission, and belongs to the technical field of converters. The wireless power transmission series DC-AC converter comprises a parallel converter and 3 high-frequency modules; the public direct-current bus is connected to a direct-current port of the grid-connected converter, and an alternating-current port of the grid-connected converter is connected with a power grid node; the input of the wireless power transmission series DC-AC converter is a public direct current bus, and the output of the wireless power transmission series DC-AC converter is connected in series between a power grid side node and a load side node; the invention realizes the direct current isolation of the serial-parallel connection side by using the wireless power transmission serial DC-AC converter based on high-frequency isolation, improves the insulation strength of the serial connection side, improves the integral compensation effect of the UPQC system, and improves the power density of the device and the utilization rate of the compensation device.

Description

Unified power quality regulator based on wireless power transmission
Technical Field
The invention relates to a unified power quality regulator based on wireless power transmission, and belongs to the technical field of converters.
Background
With the rapid development of national economy, more and more sensitive users and important equipment are connected into a power distribution network, and higher requirements are put on the electric energy quality of the power distribution network; the problems of voltage sag, voltage flashover and the like caused by instantaneous faults of the power distribution network are obvious, and the safety and the reliability of power application are seriously influenced.
At present, external power electronic compensation devices such as an Active Power Filter (APF), a static reactive power generator (STATCOM), a Dynamic Voltage Restorer (DVR) and the like which are common in the market adjust the quality of electric energy. The APF has a good effect of improving current harmonics, but cannot improve voltage quality, and in recent years, equipment tripping is caused by power grid voltage fluctuation; although STATCOM and DVR can solve voltage fluctuation, the current harmonic compensation can not be realized; a Unified Power Quality Conditioner (UPQC) performs unified compensation and suppression on Power Quality problems of a Power system, such as voltage sag/rise, voltage fluctuation, reactive Power, harmonics, and the like. The conventional scheme adopts two inverters which are interconnected at a direct current side and are respectively connected in parallel and in series with a power distribution network, can simultaneously realize the comprehensive treatment of voltage quality and current harmonics, but uses a power frequency transformer to isolate and compensate the sudden rising and falling of the system voltage, has larger volume and lower efficiency.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a unified power quality regulator based on wireless power transmission, which utilizes a high-frequency isolation DC-AC converter to improve the power density of a device, utilizes the wireless power transmission to improve the isolation pressure-resistant strength and simplify the structural design, improves the compensation effect of a UPQC system and improves the utilization rate of a compensation device.
In order to achieve the purpose, the invention adopts the technical scheme that:
a unified power quality regulator based on wireless power transmission is characterized by comprising a parallel converter and a wireless power transmission series DC-AC converter;
the input end of the wireless electric energy transmission series DC-AC converter is connected with a common direct current bus node P + and a common direct current bus node N-, and the three-phase output end is respectively connected between a power grid node and a load side node in series;
the direct current ports of the parallel converters are connected to the nodes P + and N-of the public direct current bus, and the alternating current ports of the parallel converters are connected to the node A of the power grid1、B1、C1、N；
The parallel converter is built by 8 IGBT tubes, a direct current capacitor and 4 filters;
the wireless power transmission series DC-AC converter is composed of 3 identical high-frequency modules, each high-frequency module is composed of 1 half bridge, 1 bidirectional power device H bridge, an isolation transformer and an LCL filter, and the isolation transformer is a high-frequency isolation transformer.
Furthermore, every two IGBT tubes in the parallel converter form a half bridge, the total number of the half bridges is four, the neutral point of each half bridge is respectively connected with one end of each of 4 filters, and the other ends of the 4 filters are respectively connected with a power grid node A1、B1、C1N; the collectors of the upper half-bridge IGBT tubes in the four half-bridges are connected to a positive node P + of a common direct current bus, the emitters of the lower half-bridge IGBT tubes in the four half-bridges are connected to a negative node N-, a direct current capacitor C is connected between the nodes P + and N-pThe A, B, C three-phase filter may be of the L, LC or LCL type, and the N-phase filter of the L type.
Further, the wireless power transmission series DC-AC converter has the following structure: 2 MOSFET transistors Qx1、Qx22 capacitors C forming the left half-bridge of the primary side of the DC-AC converterx1、Cx2Forming a primary side right half-bridge of the DC-AC converter; MOSFET Qx1Drain electrode and capacitor Cx1The positive electrodes of the two-way switch are connected to a common direct current bus positive node P +; MOSFET Qx2Source and capacitor Cx2The negative poles of the two half-bridges are connected to a positive node N of a common direct current bus, and neutral points of a left half-bridge and a right half-bridge of the primary side are respectively connected to a primary side homonymous end of an isolation transformer and a series compensation capacitor Cxr1One end of (A), Cxr1One end of the transformer is connected with the non-homonymous end of the primary side of the transformer;
the secondary side of the converter is composed of 8 MOSFET tubes Sxa1-Sxa4、Sxb1-Sxb4Form an alternating current H bridge, and every 2 MOSFET tubes Sxay、SxbyThe reverse connection forms an AC power device pair, 4 AC power device pairs form an AC H bridge, and P of the AC H bridge1And N1Connecting the same-name end of the secondary side of the isolation transformer with a series compensation capacitor Cxr2One end of (A), Cxr2One end of the AC H bridge is connected with the non-homonymous end of the transformer, the central points of the left and right bridge arms of the AC H bridge are respectively connected with one end of the inductance of the LCLx filter and one end of the filter capacitor, and the LCLx filterThe other end of the filter inductor is connected with a power grid node, and the filter capacitor is connected with a load side node;
x = a, b, c above; y =1,2,3, 4.
Furthermore, the isolation transformer is a loose coupling transformer without a corresponding magnetic core, in order to improve the transmission efficiency, the two ends of the isolation transformer adopt series compensation, and a capacitor C is added between the non-homonymous end of the transformer and the converterxr1And Cxr2Where x = a, b, c.
Further, the wireless power transmission is connected with the Q at the DC side of the DC-AC converter in seriesx1、Qx2A high frequency PWM signal control with 50% duty cycle, where x = a, b, c, for controlling the alternating conduction of 2 MOSFETs in the half bridge on the DC side of the high frequency module, the phase of the half bridge on the parallel side leading the phase of the half bridge on the series side when energy is transferred from the parallel side to the series side; conversely, when energy is transferred from the series side to the parallel side, the phase of the parallel side half bridge lags the phase of the series side half bridge.
Further, the wireless power transmission is connected with 8 MOSFET tubes S on the AC side of the DC-AC converter in seriesxa1-Sxa4、Sxb1-Sxb4Different operating frequencies, where x = a, b, c, Sxa1And Sxb3Synchronization, Sxb1And Sxa3Synchronization, Sxa1And Sxa3Driven by PWM signals at power frequency and opposite signals, where Sxa1And Sxb3Power frequency positive half cycle is always conducted, Sxb1And Sxa3The power frequency negative half cycle is always conducted; sxa4And Sxb2The power frequency negative half cycle is always driven by a locking PWM signal, the power frequency positive half cycle is driven by a high-frequency PWM signal with a variable duty ratio, the high-frequency PWM signal is generated by SPWM, a modulation wave is a positive half cycle signal of which the AC side needs to output voltage, and a carrier wave is a triangular wave; sxb4And Sxa2The positive half cycle of power frequency is always driven by the locking PWM signal, the negative half cycle of power frequency is driven by the high-frequency PWM signal with variable duty ratio, the high-frequency PWM signal is generated by SPWM, the modulation wave is obtained by inverting the negative half cycle signal of AC side needing output voltage, and the carrier wave is triangular wave.
Furthermore, the wireless power transmission series DC-AC converter compensates a series voltage according to the voltage requirement of the load side in real time, and the series voltage and the voltage of the power grid side form a synthesized voltage to be supplied to the load.
Has the advantages that:
the UPQC adopts a series compensation scheme of high-frequency isolation, so that the volume of the converter is reduced, and the isolation withstand voltage and the flexibility can be improved by adopting a wireless electric energy transmission mode.
The method has the following specific advantages:
1. the DC-AC converter is used for replacing the traditional transformer isolation, so that the power density of the device is improved;
2. the DC-AC converter is independently arranged on a non-DC side, and the voltage of the DC-AC converter is directly controlled by using the high-frequency DC-AC converter, so that the control of the inverter side is simplified;
3. the MOSFET of the DC-AC converter operates at ZVS, the switching loss is low, and the efficiency is high;
4. the invention adopts a modular design, and simplifies the circuit layout.
Drawings
The invention will be further explained with reference to the drawings, in which:
fig. 1 is a schematic diagram of the structure of the present invention.
Fig. 2 is a schematic diagram of a parallel converter in an embodiment of the invention.
Fig. 3 is a schematic diagram of an a-phase high-frequency module in the embodiment of the present invention.
Fig. 4 is a diagram of phase shift control pulses of a DC-AC converter in an embodiment of the present invention.
Fig. 5 is a voltage and current compensation phasor diagram of the UPQC with inductive load in an embodiment of the invention.
Fig. 6 is a voltage and current compensation phasor diagram of the UPQC with capacitive load in an embodiment of the invention.
Fig. 7 is a UPQC power flow diagram in an embodiment of the present invention.
Detailed Description
The invention is described in detail below with reference to the figures and the specific embodiments. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
Referring to fig. 1, the present invention provides a unified power quality regulator based on wireless power transmission, which includes a parallel converter, a wireless power transmission series DC-AC converter; the input end of the wireless electric energy transmission series DC-AC converter is connected with a common direct current bus node P + and a common direct current bus node N-, and the three-phase output end is respectively connected between a power grid node and a load side node in series; the direct current port of the grid-connected converter is connected to the nodes P + and N-of the public direct current bus, and the alternating current port of the grid-connected converter is connected to the node A of the power grid1、B1、C1、N。
Referring to the attached figure 2, the parallel converter is built by 8 IGBT tubes, a direct current capacitor and 4 filters, every two IGBT tubes in the parallel converter form a half bridge, the total number of the half bridges is four, a neutral point of each half bridge is respectively connected with one end of each of the 4 filters, and the other end of each of the 4 filters is respectively connected with a power grid node A1、B1、C1N; the collectors of the upper half-bridge IGBT tubes in the four half-bridges are connected to a positive node P + of a common direct current bus, the emitters of the lower half-bridge IGBT tubes in the four half-bridges are connected to a negative node N-, a direct current capacitor C is connected between the nodes P + and N-pThe A, B, C three-phase filter may be of the L, LC or LCL type, and the N-phase filter of the L type.
The wireless power transmission series DC-AC converter is composed of 3 identical high-frequency modules shown in figure 3, and each high-frequency module is composed of 1 half bridge, an H bridge composed of 1 bidirectional power device, a high-frequency isolation transformer and an LCL filter. The structure of each phase of high-frequency wireless power transmission series DC-AC converter is as follows:
2 MOSFET transistors Qx1、Qx2(wherein the variable x = a, b, C) forms a primary side left half bridge of the DC-AC converter, and 2 capacitors Cx1、Cx2(wherein the variable x = a, b, c) constitutes the DC-AC converter primary right half-bridge; MOSFET Qx1(wherein variable x = a, b, C) drain and capacitance Cx1(where the positive poles of the variables x = a, b, c) are both connected to a common dc bus positive node P +; MOSFET Qx2Source of (where variable = a, b, C) and capacitance Cx2The cathodes of (x = a, b, c) are all connected to a commonA positive node N-of the direct current bus, and neutral points of the primary left half-bridge and the primary right half-bridge are respectively connected to a primary dotted end of the isolation transformer and a series compensation capacitor Cxr1(where variable x = a, b, C) one end, Cxr1One end of (x = a, b, c) is connected with a non-homonymous end of the primary side of the transformer;
the secondary side of the converter is composed of 8 MOSFET tubes Sxa1-Sxa4、Sxb1-Sxb4(where the variable x = a, b, c) constitutes an ac H-bridge, each 2 MOSFET tubes Sxay、Sxby(wherein, the variable x = a, b, C; y =1,2,3,4) are reversely connected to form an AC power device pair, 4 AC power device pairs form an AC H bridge, and P1 and N1 of the AC H bridge are connected with a same-name end of a secondary side of an isolation transformer and a series compensation capacitor Cxr2(where variable x = a, b, C) one end, Cxr2The center points of the left and right bridge arms of the alternating current H bridge are respectively connected with one end of a filter inductor of the LCLx (wherein variable x = a, b, c) and one end of a filter capacitor, the other end of the filter inductor of the LCLx (wherein variable x = a, b, c) is connected with a power grid node, and the filter capacitor is connected with a load side node.
Referring to fig. 3, the isolation transformer of the high-frequency DC-AC converter is a loosely coupled transformer without a corresponding magnetic core, in order to improve the transmission efficiency, series compensation is applied to two ends of the isolation transformer, and a capacitor C is added between the non-homonymous end of the primary side and the secondary side of the transformer and the converterxr1And Cxr2(where variable x = a, b, c).
Referring to fig. 4, the wireless power transmission is connected in series with the Q of the DC side of the DC-AC converterx1、Qx2Wherein the variable (x = a, b, c) is controlled with a high frequency PWM signal of 50% duty cycle for controlling the alternating conduction of the 2 MOSFETs in the half-bridge on the DC side of the high frequency module, the phase of the half-bridge on the parallel side leading the phase of the half-bridge on the series side when energy is transferred from the parallel side to the series side; conversely, when energy is transferred from the series side to the parallel side, the phase of the parallel side half bridge lags the phase of the series side half bridge. 8 MOSFET tubes S on AC side of high-frequency DC-AC converterxa1-Sxa4、Sxb1-Sxb4(where the variables x = a, b, c) differ in the operating frequency, Sxa1And Sxb3Synchronization, Sxb1And Sxa3Synchronization, Sxa1And Sxa3Driven by PWM signals at power frequency and opposite signals, where Sxa1And Sxb3Power frequency positive half cycle is always conducted, Sxb1And Sxa3The power frequency negative half cycle is always conducted; sxa4And Sxb2The power frequency negative half cycle is always driven by a locking PWM signal, the power frequency positive half cycle is driven by a high-frequency PWM signal with a variable duty ratio, the high-frequency PWM signal is generated by SPWM, a modulation wave is a positive half cycle signal of which the AC side needs to output voltage, and a carrier wave is a triangular wave; sxb4And Sxa2The positive half cycle of power frequency is always driven by the locking PWM signal, the negative half cycle of power frequency is driven by the high-frequency PWM signal with variable duty ratio, the high-frequency PWM signal is generated by SPWM, the modulation wave is obtained by inverting the negative half cycle signal of AC side needing output voltage, and the carrier wave is triangular wave.
Referring to fig. 5 and 6, the wireless power transmission series DC-AC converter compensates a series voltage according to the voltage requirement of the load side in real time, and forms a combined voltage with the voltage of the grid side to provide a load with high voltage quality requirement. The specific principle is shown in fig. 5 and 6:
if in-phase compensation is adopted, the active component of the load current fundamental frequency can be obtainedI L1 And system voltage U sag In phase, thus
Figure DEST_PATH_IMAGE001
(1)
Wherein the content of the first and second substances,S L 、φ L respectively, load capacity and load power factor angle.
If in-phase compensation is not adopted, namely the load current fundamental frequency active componentI L1 And system voltageU sag The phases are different, and at the moment, the UPQC can compensate reactive components on the serial side, so that the control of load power flow is realized; if the load current has active component at fundamental frequencyI L1 And system voltageU sag The opposite phase compensates a series voltage with opposite phase, which effectively limitsThe voltage of the load side, therefore, when the short-circuit fault occurs on the load side, the short-circuit current can be effectively reduced through UPQC control.
Fig. 7 is a flow chart of active power in the system when a voltage sag occurs. During temporary drop, on one hand, the serial and parallel sides release the stored energy to provide active power supplement for the system, and on the other hand, the parallel side absorbs the active power from the system to maintain the stability of the direct current bus voltage. Neglecting inverter losses, thus
Figure 716320DEST_PATH_IMAGE002
(2)
In the formula (I), the compound is shown in the specification,P S、P Lrespectively the active power of the system side and the load side;P C1、P C2active power absorbed and output from the system to the system by the UPQC respectively;P SC、P PCactive power is output to the series side and the parallel side of the UPQC respectively.
When the voltage sag amplitude is small and the sag duration is short in formula (2), the method comprises the following stepsP C1=P C2At this time, the active current of the parallel sidei pStill operating within its limits; when the voltage sag amplitude is larger and the sag duration is longer, the system needs the energy storage and release of the UPQC capacitor to provide more energy compensation, at this time, in order to avoid the overcurrent of the switching device and ensure the normal operation of the serial side,i prun to the limit value ofP C1≤P C2。
If the voltage swell needs to be compensated or the fault current is limited, on one hand, energy needs to be absorbed by the parallel connection side in series connection, meanwhile, the parallel connection side releases stored energy to be system feedback active power, and on the other hand, the parallel connection side controls and maintains the stability of the voltage of the parallel connection side direct current bus.
The parallel converter mainly realizes active power control, reactive compensation and stabilization of power balance between the parallel side and the series side, compensates voltage components and harmonic components of transverse and longitudinal axes in real time, realizes comprehensive treatment of voltage and current electric energy quality, realizes weak coupling correlation between the series converter and the parallel converter, and prolongs the compensation time of voltage drop. The series converter realizes voltage compensation, inhibits fault current, improves voltage and power quality, and is matched with a dispatching system to participate in certain power flow control.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (7)

1. A unified power quality regulator based on wireless power transmission is characterized by comprising a parallel converter and a wireless power transmission series DC-AC converter;
the input end of the wireless electric energy transmission series DC-AC converter is connected with a common direct current bus node P + and a common direct current bus node N-, and the three-phase output end is respectively connected between a power grid node and a load side node in series;
the direct current ports of the parallel converters are connected to the nodes P + and N-of the public direct current bus, and the alternating current ports of the grid-connected converters are connected to the node A of the power grid1、B1、C1、N；
The parallel converter is built by 8 IGBT tubes, a direct current capacitor and 4 filters;
the wireless power transmission series DC-AC converter is composed of 3 identical high-frequency modules, each high-frequency module is composed of 1 half bridge, 1 bidirectional power device H bridge, an isolation transformer and an LCL filter, and the isolation transformer is a high-frequency isolation transformer.
2. The unified power quality regulator based on wireless power transmission as claimed in claim 1, wherein each two IGBT transistors in the parallel converter form a half-bridge, and there are four half-bridges in total, the neutral point of each half-bridge is connected to one end of each of 4 filters, and the other end of each of 4 filters is connected to grid node a1、B1、C1N; the collectors of the IGBT tubes of the upper half-bridges in the four half-bridges are connected to a positive node P + of a common direct current bus, and the lower half-bridges in the four half-bridgesThe emitter of the IGBT tube is connected to a negative node N-of the common direct current bus, and a direct current capacitor C is connected between the nodes P + and N-pThe filter may be in the form of L, LC or an LCL.
3. The wireless power transmission-based unified power quality conditioner of claim 1, wherein the wireless power transmission series DC-AC converter structure is as follows:
2 MOSFET transistors Qx1、Qx22 capacitors C forming the left half-bridge of the primary side of the DC-AC converterx1、Cx2Forming a primary side right half-bridge of the DC-AC converter; MOSFET Qx1Drain and capacitor Cx1The positive electrodes of the two-way switch are connected to a common direct current bus positive node P +; MOSFET Qx2Source and capacitor Cx2The negative poles of the two half-bridges are connected to a positive node N of a common direct current bus, and neutral points of a left half-bridge and a right half-bridge of the primary side are respectively connected to a primary side homonymous end of an isolation transformer and a series compensation capacitor Cxr1One end of (A), Cxr1One end of the transformer is connected with the non-homonymous end of the primary side of the transformer;
the secondary side of the converter is composed of 8 MOSFET tubes Sxa1-Sxa4、Sxb1-Sxb4Form an alternating current H bridge, and every 2 MOSFET tubes Sxay、SxbyThe reverse connection forms an alternating current power device pair, 4 alternating current power device pairs form an alternating current H bridge, and P1 and N1 of the alternating current H bridge are connected with a same-name end of a secondary side of the isolation transformer and a series compensation capacitor Cxr2One end of (A), Cxr2One end of the LCLx filter is connected with a non-homonymous end of the transformer, the central points of a left bridge arm and a right bridge arm of the alternating current H bridge are respectively connected with one end of an LCLx filter inductor and one end of a filter capacitor, the other end of the LCLx filter inductor is connected with a power grid node, and the filter capacitor is connected with a load side node;
the variable x = a, b, c; y =1,2,3, 4.
4. The unified power quality regulator based on wireless power transmission as claimed in claim 1 or 3, wherein the isolation transformer is a loosely coupled transformer without corresponding magnetic core, and for improving transmission efficiency, the two ends of the isolation transformer are connected in seriesCompensation, adding capacitor C between non-homonymous terminal of transformer and converterxr1And Cxr2，Where the variable x = a, b, c.
5. The wireless power transmission-based unified power quality conditioner of claim 3, wherein the wireless power transmission is connected in series with the Q of the DC side of the DC-AC converterx1、Qx2(x = a, b, c) is controlled with a high frequency PWM signal of 50% duty cycle for controlling the alternating conduction of the 2 MOSFETs in the half-bridge on the DC side of the high frequency module, the phase of the half-bridge on the parallel side leading the phase of the half-bridge on the series side when energy is transferred from the parallel side to the series side; conversely, when energy is transferred from the series side to the parallel side, the phase of the parallel side half bridge lags the phase of the series side half bridge.
6. The wireless power transmission-based unified power quality regulator according to claim 3, wherein the wireless power transmission is connected in series with 8 MOSFET S tubes on AC side of DC-AC converterxa1-Sxa4、Sxb1-Sxb4The operating frequencies are different, with the variable x = a, b, c, Sxa1And Sxb3Synchronization, Sxb1And Sxa3Synchronization, Sxa1And Sxa3Driven by PWM signals at power frequency and opposite signals, where Sxa1And Sxb3Power frequency positive half cycle is always conducted, Sxb1And Sxa3The power frequency negative half cycle is always conducted; sxa4And Sxb2The power frequency negative half cycle is always driven by a locking PWM signal, the power frequency positive half cycle is driven by a high-frequency PWM signal with a variable duty ratio, the high-frequency PWM signal is generated by SPWM, a modulation wave is a positive half cycle signal of which the AC side needs to output voltage, and a carrier wave is a triangular wave; sxb4And Sxa2The positive half cycle of power frequency is always driven by the locking PWM signal, the negative half cycle of power frequency is driven by the high-frequency PWM signal with variable duty ratio, the high-frequency PWM signal is generated by SPWM, the modulation wave is obtained by inverting the negative half cycle signal of AC side needing output voltage, and the carrier wave is triangular wave.
7. The wireless power transmission-based unified power quality regulator of claim 1, wherein the wireless power transmission series DC-AC converter compensates a series voltage according to the requirement of the load side voltage in real time, and forms a synthesized voltage with the grid side voltage to supply to the load.
CN202110606060.8A 2021-06-01 2021-06-01 Unified power quality regulator based on wireless power transmission Pending CN113224759A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114362569A (en) * 2021-11-10 2022-04-15 四川旷谷信息工程有限公司 Motor train unit ground power supply sharing direct-current bus and control method thereof

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114362569A (en) * 2021-11-10 2022-04-15 四川旷谷信息工程有限公司 Motor train unit ground power supply sharing direct-current bus and control method thereof
CN114362569B (en) * 2021-11-10 2023-08-15 四川旷谷信息工程有限公司 EMUs ground power supply sharing direct current bus and control method thereof

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